1. Field of the Invention
The present disclosure relates to feed-through elements in general, but in particular to improved feed-through elements which are capable to be used in harsh environments with high operation or emergency temperatures above 260 degrees Celsius (° C.). In particular, the feed-through elements of the present disclosure can withstand operational and/or emergency pressures above 42000 pounds per square inch (psi). Therefore they can be used in a variety of applications, especially in downhole drilling equipment as well as in the safe containment of toxic matter and in spacecrafts.
2. Description of Related Art
Feed-through elements in general are well known in the art and are incorporated in a lot of devices. In general terms, such feed-through elements usually comprise an electrical conductor which is fixed within a feed-through opening by an electrically insulating material. The parameters which characterize the performance of such feed-through devices are mainly the electrical resistance of the insulating material, the capabilities to withstand heat and pressure which tends to let the insulating material and/or the conductor burst out of the feed-through access opening.
Although such feed-through elements represent a very suitable technology to guide e.g. electrical current through the housing of devices, the parameters often limit the possible application areas in which devices which contain such feed-through elements can be used. In U.S. Pat. No. 5,203,723 feed-through elements are described which are built from a metal pin which is surrounded by a polymer material as electrically insulating material. The geometry of the polymer material which surrounds the electrical conductor is adapted to withstand higher pressures by means of recesses and protrusions such as shoulders. The described feed-through elements are used for making connections within a sonde of a downhole oil well measuring or logging tool and can be used at operational temperatures above 260° C. and pressures of at maximum 28000 psi. The volume resistance of the used polymers is about 8.0×1014 Ωcm and therefore considerably excellent. However, the long term stability of such polymers is decreased with the time of the exposure to higher operational temperatures, the exposition to electromagnetic radiation such as UV or gamma radiation and also the mechanical degradation due to physical abrasion.
Feed-through elements which contain an inorganic material such as glass as electrically insulating material are also known. U.S. Pat. No. 8,397,638 describes e.g. a feed-through device of an airbag igniter, in which the access hole of a metal support body is sealed by a glass material which also holds a pin as electrical conductor. Such feed-through elements are designed to withstand the pressure of the explosive when the igniter is fired, whereas pressures about 1000 bar which correspond to 14500 psi might be observed. The electrical properties of the insulation material are not described, but it can be assumed that the electrical volume resistance of the glass material does not play a major role because the igniter is only fired once with a short electrical pulse and then the device is destructed.
Feed-through elements as described are not sufficient for applications in harsh environments, e.g. downhole drilling devices, which facilitate the exploration and/or exploitation of natural oil and/or gas resources in increasing depths and therefore are exposed to higher operational temperatures for a longer period of time. Against this background, it is an object of the present disclosure to provide a feed-through element which is suitable for use at temperatures above 260° C. and secures high electrical insulation properties of the conductor against its surrounding.